Electrical switching system



Oct. 8, 1940.

J. F. MACKENZIE ELECTRICAL SWITCHING SYSTEM Filed July 22, 1957 UNIT INVENTOR. JOHN FRANCIS MACKENZ/E ATTORNEY.

Patented Oct. 8, 1940 2,217,064 ELECTRICAL SWITCHING SYSTEM John Francis Mackenzie, Liverpool, England, as; signor to Associated Telephone & Telegraph Company, Chicago, 111., acorporation of Delaware Application July 22, 1937, Serial No. 155,043

In Great Britain August 24, 1936 11 Claims.

The present invention relates to electrical switching systems and is more particularly concerned with systems in which control is effected jointly by members operated at fixed times and by members operated due to some variable factor. Such an arrangement may find advantageous application for the control of street lighting from a central point in accordance with the strength of daylight and also with a modification at some fixed time. In one system of this charenter the responding units associated with the individual lighting fixtures are of the three-position type giving respectively all the light on, a fraction of the lights on and all the lights off. The required results may readily be obtained by a combination of time-switch and photo-electric cell control provided the photo-electric cell is prevented from coming into action during periods of unexpected darkness within the daylight hours. It is desirable however that the street lighting should come into action at such times and diiliculties are then encountered which it is the object of the invention to overcome.

Accordingto one feature of the invention in 25 an electrical switching system for operating responding devices through a cycle in response to control at a fixed time and also due to a variable factor, if the variable factor effects a switching operation additional to that normally required to complete the cycle the responding devices are advanced through the remaining steps of the cycle so that they shall be in a position to respend satisfactorily to the fixed time control.

According to another feature ofthe invention 5 in an electrical switching system including threeposition' responding devices with on and oil positions controlled dependent on external conditions and an intermediate position. controlled independently of external conditions, if the external 40 conditions cause the dependent control to operate more frequently than normally the responding devices are additionally operated automatically corresponding to the independent control. A further feature of the invention is that in an 5 electrical switching system for the control of street lighting by switching of! and on under photo-cell control and partially of! under timewhich responding'units associated with the individual lighting fixtures are operated by high frequency currents transmitted over the supply network from a transmitter conveniently located at a substation. This transmitter may be of the type employing a mercury spark gap and ar- 10 ranged to be energised by the closing of a con-- tactor when a signal is to be transmitted. The signals are assumed to be all of the same character whichever switching operation in the cycle is required. l 15 Such a system of street lighting with centralized control is known,"for instance, in the British Patent #435,564, accepted September 24, 1935, and a switching device, such as referred to in the above patent, may be here used. The 20 mechanism of this device is shown in the British Patent #435,349, accepted July 5, 1935. Any such three-step switching device may be applied, and I have shown the same diagrammatically in the present drawing of a three-step cam for closing pairs of springs consecutively.

Under normal daylight conditions the equipment will be in the unoperated position as shown on the drawing. The direct current supply which is indicated by positive and negative signs in a circle may be simply obtained by full wave rectiilcation of the mains supply as indicated. in the upper left-hand corner while the contactor TC may be directly energised from the mains.

Immediately the daylight intensity falls to a predetermined value, a photo-electric cell device P is arranged to function in a well-known manner to bring about the operation of relay 8 and consequent closing of contacts PE. The closing of contacts PE completes acircuit for relay SA by way of contact pmi. Relay SA upon operating, at contacts sai, closes an obvious circuit for relay SB, which in turn closes a circuit for relay SC at contacts sbi. These three relays are made somewhat slow to release by a copper slug mounted on the coil-core at the end opposite the armature. At contacts sci, relay SC closes an obvious circuit for the transmitter contactor TC, the circuit including power supply conductors H and N. The contactor TC thereupon closes a power supply circuit over the same conductors to the signal generator G, which, by way of transformer Tl, transmits a high frequency signal pulse over the neutral conductor N.

Contacts scl are opened by the operation of relay SC but perform no useful function at this time. Contacts so! are opened at this time to prevent the operation of relay AM upon the operation of relay PM if relay S had meanwhile released; At contacts 304 a circuit is closed from positive at contacts PE through contacts s04 to the winding of relay PM, which thereupon operates. Relay PM closes a locking circuit for itself by way of contacts pml connected in multiple with contacts s04. 'At contacts pmZ a circuit is prepared for the energization of relay AM when relays SC and S subsequently release. break contacts of this contact set pm2, the original operating circuit for relay SA is opened so this relay releases followed in turn by relays SB and SC.

During the time that relay SC has been operated, the signal generator G has been effective to transmit a high-frequency tone signal over the neutral conductor of the power supply line to energize the check switch CS to advance the cam associated therewith by one step. This high frequency impulse is also effective to adapt other switches, similarly connected and located at var.- ious points in the network, to perform certain switching operations. The switching operation may for instance cause the illumination of all of the street lamps connected to the network.

Returning now to a discussion of the operations which take place upon the release of relay SC, it will be seen that contacts scl open the circuit to the contactor TC to terminate the high frequency impulse produced by the signal generator ,6. Contacts s02 close a circuit for relay AM, which, however, is at this time short circuited by the positive potential connected to contacts PE. Contacts s03 reclose a point in the circuit including contacts pm3 and contacts of the check switch CS which, however, is of no effect at this time, since the circuit is maintained open by contacts pm3. Contacts s04 open the original energizing circuit for relay PM, which, however, remains energized by way of its own contacts pml. At this time the transmitting equipment has completed one third of its cycle of operation with relays S and PM operated and the check switch CS advanced one step to close contacts csl, cs2, and cs3.

The other switches located at the various points in the network are all three-step switches similar to the switch CS and one of these is shown at CS with its cam operated by the magnet CS. The contacts operated by the cam at the distant station are shown as closing the lead from conductor I0 through two lamps L and L to conductor N when both spring stations are closed on the first step of the cam, for opening the circuit of lamp L on the second step thereof, and for then opening the circuit of the other lamp on. the third step.

At midnight or other suitable time it is arranged for one of the two lamps located on each standard to be switched off, this operation being controlled by the use of a time-switch which at the predetermined time closes its contacts TS for a brief period and thereby re-operates the contactor TC. This again causes a high frequency pulse to be connected to the supply mains whereupon all the responding units such as CS are advanced a further step and extinguish one of the lamps on each standard. Switch CS is also operated and contacts cs2 and cs3 are separated, contacts csl and 032 still remaining made.

At daybreak the photo-cell again comes into operation and opens the contacts PE whereupon relay AM operates in series with relay PM, the

At the latter relay holding operated, in a circuit including the winding of relay AM, contacts ;c2, pmZ and pml, and the winding of relay PM. Relay AM is preferably made slow-to-operate to prevent false operation on a momentary opening of contacts PE. On operation of relay AM, relays SA, SB and SC are again operated in turn by the closing of contact aml, the contactor again energised and the responding units such as CS advanced a further step into the normal position at which time all lights are switched off. Relay CS also responds and opens all its contacts csl, 2 and 3. Relay SC upon operating releases relays AM and PM at contacts 082 and the former relay at contact aml releases relays SA, SB and SC so that all the apparatus is restored to normal.

It will now be assumed that there is a period of premature darkness which is sufficient to warrant the lighting of the street lamps. At the commencement of this period the photo-cell comes into operation and closes contacts PE whereupon relays SA, SB, SC and PM are operated, a high frequency signal is sent, contacts csl, 2 and 3 are closed and the two lamps such as L and L on each standard are switched on in the normal manner. On operation of relay PM relays SA, SB and SC are released and relay PM looks as before to the PE contacts. Should the light intensity again increase sufficiently before the normal hour of dusk orindeed at any time before the time switch comes into operation, the opening of contacts PE will operate relay AM in series with relay PM. It is now necessary to deliver two pulses to the contactor in order to restore the responding devices to normal. Relay AM upon operating operates relays SA, SB and SC as before whereupon the contactor TC is energised to transmit a second high frequency impulse over the neutral conductor of the power supply main and all responding units including the check switch CS are stepped forward to the second position. In this state contacts csl and cs2 only remain closed and one lamp on each standard is switched off. Relay SC upon operating releases relays AM and PM whereupon relays SA, SB and SC are released in turn. On release of relay SC however relay SA is now again energised over contacts s03, pmi, csl and cs2 whereupon relays SB and SC will be operated in turn. Relay SC therefore again energises the contactor and all responding units are advanced to the normal position. All lamps are then switched off and contacts csl and cs2 open and release relays SA, SB and SC whereupon the equipment is again in normal condition.

The invention herein described thus provides a simple means whereby in a centralised streetlighting control system with so-called halfnight" switching facilities the additional advantages of automatic control by variation in day light intensity are obtained.

I claim:

1. In a system for controlling the operation of a switching device through a fixed three-position cycle, means for initiating the operation of said device to the first position of the cycle, means effective while said first-named means is effective, to operate said device to the second position of the cycle, and means controlled by said firstnamed means for operating'said device to the third position of the cycle.

2. In a system for controlling the operation of a switching device through a fixed three-position cycle, means for initiating the operation of said device to the first position of the cycle, means effective while said first-named means is effective, to operate said device to the second posimeansforadvancingsaidswitchingdevicetoa' 2,917,004 tion of the cycle, aud means controlled by said first-named means for operating .said device to the third position of the cycle. all of said means being so arranged as to cause the operation of said device through a complete cycle regardless of the order of operation of said first and second means. v

3. In a system for controlling the operation of a switching device to one of a plurality of positions, illumination controlled means for operating said device to a first position, and a time switch for operating said device to a second position, said illumination controlled means being subsequently effective to restore said device to its original position.

' 4. In a system for controlling the operation of switching devices over an electric power distribution network, means eifective' upon the operationv of an illumination-responsive device to transmit an impulse over said network to open ate all of said switching devices to a first position, said meansbeing-eflective upon the release of said illumination-responsive device to transmit a second impulse over said network to operate said switching devices to a second position and to transmit a third impulse-independent of said illumination-responsive device to restore said 6. In a system for controlling the operation-of.

multi-position switching devices, means operated by the operation of a light-responsive device, means operated by said first-named means for generating an impulse to advance said switching devices to a first position, means for releasing said last-named means independent of said lightresponsive device to terminate the impulse means independent of said light-responsive device and said first-named means for momentarily reoperating said impulse generating means to advance said switching devices to a second position, and means for reoperating said first-named means upon the release of said light-responsive device to effect the advance of said switching devices to a third position. i

'7. Inasystemforcontrollingtheoperationof a multi-position switching device, circuit closing means controlled by a" photo-electric device means operated by said circiiit'closing means to advance said switching device tea first position,

seecndpositionwhensaideircuitclosingmeans restcraandmeansccntrolledbysiidswitching device to a third position independent of said circuit closing means.

device in its second position for advancing said v8. In a system for controlling the operation of v a multi-position switching device, first circuitclosing means, means operated by said first circuit-closing means to move said device to one po-.

sition, second circuit-closing means arranged to move said device to another position,'and means operated by the release of said first circuit-closoperated by the release of said first circuit-closing means to move said device toa third position,

and means controlled by said device in said other position and efiective only in case said first circult-closing means operates and releases before said second circuit-closing means to move said device to said third position.

10. In a switching system; a multi-position step-by-step switching device; 'a first circuit-closing device; a second circuit-closing device; means for advancing said switching device one step each time said first circuit-clodng device operates, each time said second circuit-closing device operates, and each time said first circuit-closing device releases, independent of the order of operation thereof; means eilective in case said first circuit-closing device operates and releases to advance said switching device only two steps before said second circuit-closing device operates, to advance said switching device a further step, said last-named means effective in case said second circuit-closing means operatesto advance said switching deviceonly one step before said first circuit-closing device operates and releases, to advance saidswitching device two further steps.

11. In a switching system; a multi-position unidirectional step-by-step switching device having a normal position and two off-normal positions; a first circuit-closing device; a second circuit-closing device; means for advancing said switching device to a first ofl-normal position in, response to the operation of either oi said circuitclosing devices,'said second circuit-closing device being eifective to advance said switching device to a second off-normal position in case said first circuit-closingdevice has not released. said first circuit-closing device being eflectiveto advance said switching device to a second off-normal posi- 4 tion in case said second circuit-closing device has not operated; and means controlled by said switching device eil'ective to advance said device to its normal position if said second circuit-closing device operates before said first circuit-closing device. or if said first circuit-closing device operates and releases before said second circuitclosing device operates.

l JOHN FRANCIS 

